NHTSA’s Proposed Side-Impact Testing Standard – the good, the bad and the technical

This week many of you may have heard through mainstream media outlets that NHTSA’s long-awaited “NPRM” on a Federal Side-Impact Standard for Child Restraints was about to be unveiled. Here at CarseatBlog that was practically an excuse to break out the bubbly since we’ve been waiting for this announcement since the end of summer 2013 when they promised us it was going to ready! To be honest, we’ve actually waited over a decade for this but I’d rather not remind myself how quickly the last decade has flown by. Anyhow, we didn’t want to just regurgitate a press release or some bare-bones news article with no nitty-gritty details because we know you expect more than that from us, so we sat on our fingers for a few days until the actual NPRM was released.

The proposed test is interesting in so many ways but it can be really confusing too if you don’t understand all the technicalities and nuances of what they’re proposing. My advice is not to get too fixated on anything in particular because you have to consider the whole picture. There are always going to be pros and cons and almost every upside comes at the expense of something else. It’s just the way it is.

In writing this update I was torn over whether to keep it simple or go all out and try to help you make sense of everything. The latter seemed like an overwhelming task but I’m also not a keep-it-simple-kind-of-person. In the end I compromised by doing a bit of both. I tried to outline the main points (the stuff that most people would care about) in the beginning, and then I tossed in some stuff that only the die-hards with a serious coffee or diet-soda-induced caffeine buzz could manage to get through. I hope that pleases everyone. 🙂

Quick Overview for Parents and Caregivers:

What most parents need to take away from this is that the government standards, set by the National Highway Traffic Safety Administration (NHTSA), now have just a minimum pass/fail requirement for a typical frontal crash test only. This proposed rule will add a minimum pass/fail side-impact test that manufacturers must pass in order to sell a child safety seat in the USA. Side impacts are the most deadly types of crashes to properly restrained passengers, adults and children alike. So, this testing is potentially a big step forward in protecting our littlest passengers from head injury in particular.

This proposed test would simulate a small car moving through an intersection at a low speed and being “T-boned” by another car going about 30 miles per hour. A carseat with a child-sized dummy will be measured for injury in the rear seat, on the nearest side that is struck by the simulated oncoming vehicle. Please note that this will NOT be a 5-star comparative type of rating for either crash safety or fit to vehicle; those are separate mandates that have all but disappeared from public discussion. It’s also not yet in final form, so the public has 90 days to comment before the final rule is set. For example, the proposed test omits some key scenarios, including installation with a seatbelt, installation without a top tether and installation for children using a 5-point harness above 40 pounds. These are all very important issues, especially given the shift to seatbelt use because of the new 2014 labeling required on carseats that limits the use of LATCH system, due to concerns about the strength of the hardware.

Carseats required to pass the new testing are a long way from the market. Once the final rule is passed, we probably won’t see officially compliant models for up to 3 years. Also, parents shopping for carseats in the meantime should know that many of them already adhere to voluntary side-impact testing standards and some manufacturers have incorporated side-impact protection features for years. These voluntary standards vary from one manufacturer to another and will be different from government testing, but it is important to know that some carseat manufacturers are already designing products with side-impact protection in mind.

More Details on the Proposed Rule for CPS Technicians and Advocates:

Notice of Proposed Rule Making: Amendment to FMVSS 213 – Side Impact Testing Standard

“SUMMARY: This NPRM proposes to amend Federal Motor Vehicle Safety Standard (FMVSS) No. 213, “Child restraint systems,” to adopt side impact performance requirements for all child restraint systems designed to seat children in a weight range that includes weights up to 18 kilograms (kg) (40 pounds (lb)). NHTSA is issuing this NPRM to ensure that child restraints provide a minimum level of protection in side impacts by effectively restraining the child, preventing harmful head contact with an intruding vehicle door or child restraint structure, and by attenuating crash forces to the child’s head and chest.”

 

 

In a Nut Shell:

The proposed test procedure would simulate the full-scale vehicle-to-vehicle side-impact crash replicated by FMVSS 214.

• Dynamic sled test would simulate the MDB (Movable Deformable Barrier) test of FMVSS 214 which has the striking vehicle traveling at 30 mph (48.3 km/h) impacting the struck vehicle traveling at 15 mph (24 km/h)
• Tests CR in near-side impact
• First test of its kind in the world for testing CRs in a sled system that simulates vehicle acceleration and intruding door of a small passenger car
• Door intrusion known to be a factor for moderate and severe injury in side impacts
• Proposed test based on acceleration sled system developed by Takata

 

Specifics:

• CRs for children rated up to 22 lbs would be tested with CRABI dummy
• CRs for children 22-40 lbs., including boosters, would be tested with Q3s dummy
• Forward-facing CR installed with LATCH (lower anchors and tether)
• Rear-facing CRs installed using lower anchors only
• Belt-positioning boosters (those rated for children under 40 lbs.) installed with lap/shoulder belt
• Center of CR positioned 300mm from edge of the sliding seat next to the intruding door – simulating a near-side seating position
• Armrest on door located 32mm from edge of seat towards CR

 

Rationale for limiting testing to under 40 lbs.:

• No appropriate test dummy for representing kids over 40 lbs. right now
• NHTSA determined that seated height of children over 40 lbs. is typically sufficient to take advantage of the vehicle’s side impact protection system (including curtain airbags)

 

ATDs:

• Q3s is the side-impact version of the 3-yr-old Q Series dummy developed in Europe (weighs 32 lbs.)
• CRABI – 12-month-old dummy used in current frontal crash testing (weighs 22 lbs)

 

Most parents can stop here unless they are looking to cure their insomnia! Geeks and die-hard advocates looking for in-depth commentary are warned that it’s about to get technical!

 

More on the Q3s ATD

The Q3s is built on the platform of the standard Q3 dummy series (the Q-series are frontal ATDs used in Europe), but the Q3s has enhanced lateral biofidelity, durability and additional instrumentation for specialized use in side-impact testing. The Q3s dummy features a new head and a neck that has biofidelic lateral, and frontal performance. This dummy also has a deformable shoulder with shoulder deflection measurement capabilities, a new arm with improved flesh characteristics, a laterally compliant chest and a pelvis with improved upper leg flesh, floating hip cups and a pubic load transducer.

 

Simulating a Real-World SI Crash:

“Based on the information that has become available since the 2002 ANPRM, we tentatively conclude that a side impact is best replicated if the test procedure reflects and replicates dynamic elements of both the striking and struck vehicle in a vehicle-to-vehicle crash. We believe that a side-impact test procedure should account for: (1) the struck vehicle door velocity prior to the interaction of the striking vehicle with the door sill of the struck vehicle, (2) the acceleration profile of the struck vehicle, and (3) the impact angle to replicate the longitudinal component of the direction of force. Specification of these parameters, based on actual vehicle crash characteristics, would enable the realistic simulation of the relative velocity between the intruding door and the CRS.”

The proposed test buck consists of a sliding “vehicle” seat (representative of a rear seat designated seating position) mounted to a rail system along with a “side door” structure rigidly mounted to the sled buck structure. The sliding “vehicle” seat and side door are representative of a typical modern passenger vehicle. This “Side Impact Seat Assembly” (SISA) is positioned sufficiently away from the side door to allow the sled to reach the desired velocity (31.3 km/h) prior to the time the sliding “vehicle” seat starts to accelerate to a specific acceleration profile.

Based on tests and on average impact angle computed from the vehicle’s right rear sill velocities of MDB-to-vehicle crash tests, NHTSA selected a 10-degree impact angle as the most appropriate.

NHTSA also conducted sled tests at different impact angles (0, 5, 10, and 20 degrees) using the Takata sled procedure to compare them to four MDB crash tests performed using the Q3s dummy restrained in a CR in the rear seat behind the driver. They found that a 10-degree impact angle on the sled test produced dummy responses closer to those measured by the ATD in the same CR in the four MDB crash tests than the other impact angles.

Test bench, door geometry, vehicle seat and door padding characteristics are important in a side impact test, to ensure these are representative of the vehicle rear seat environment. NHTSA identified the following rear seat features to replicate in the SISA: rear seat geometry, rear seat cushion stiffness, and door shape (height of window, armrest thickness, door padding).

• Armrest thickness (protrusion of armrest in the door) selected for the SISA sled system consists of a 64 mm (2.5 in) thick padding material attached to a 51 mm (2 in) thick door panel.
• To ensure the side impact test is sufficiently stringent to account for vehicle beltlines that are higher than the average value, NHTSA proposes a beltline height of 500 mm (19.6 in) for the SISA.

 

Proposed Injury Criteria

There is no infant test dummy available that is specially designed for side-impact testing. While the CRABI dummy is not a side impact dummy, NHTSA believes that it could be a useful tool to evaluate some aspects of CR performance in side-impacts. Even if the evaluation is limited to containment, structural integrity, and other related matters. NHTSA is proposing that CRABI be used to measure head-to-door contact only, and not HIC15 or chest acceleration.

For Q3s testing proposed injury criteria is: HIC15 ≤ 570; chest deflection ≤ 23 mm

Current FMVSS 213 frontal-impact requirement specifies an injury assessment reference value (IARV) of 1,000 measured in a 36 ms timeframe (36 ms for integrating head acceleration) (HIC36 =1,000). For this test, NHTSA is proposing a HIC limit of 570 measured in a 15 ms timeframe (15 ms duration for integrating head resultant acceleration) (HIC15=570) when using the Q3s dummy in the side-impact sled test. Injurious contacts (such as head-to door contacts) are of short duration (less than 15 ms) in this set-up and more appropriately addressed by HIC15 (15 millisecond duration for integrating head resultant acceleration) than HIC36.

NHTSA tentatively believes that there is not a need for a performance criterion that would prohibit head contact with the intruding door. Their video analysis showed that 13 out of 19 forward-facing CR models had head-to-door contact during the test. However, further analysis of the head acceleration time histories showed that the peak acceleration occurred before the head contacted the door. Six of the 13 models that had head-to-door contact had HIC15 values exceeding 570; these peak HIC15 values occurred prior to head contact with the door. This suggested that the peak head acceleration was the result of a previous impact, most likely the head contacting the side of the CRS at the time the CRS contacted the intruding door. (Four of the “convertible” CR models tested in the forward-facing mode were also tested in the rear-facing mode using the Q3s dummy; the results showed there was no head-to-door contact during these tests.) Given that the head acceleration values computed during the time of head-to-door contact were lower than the peak head acceleration, NHTSA believes that the risk of head injury from head-to-door contacts for the 13 CRs was much lower than the risk from the peak acceleration. For those reasons, they have tentatively decided not to use a performance criterion based on head contact in tests with the Q3s dummy because HIC15 appears better able to discern between “soft” non-injurious contacts and “hard” injurious contacts, and thus would be a better predictor of head injury in the side impact test.

However, NHTSA tentatively believes that the CRABI dummy would be suitable and should be used for assessing safety risks related to a CR’s ability to limit head-to-door contact in side crashes. Because the 0-to-12 month age group has the highest restraint use of any age group, NHTSA seeks to evaluate the performance of CRs for this age group in side crashes even if such evaluation is limited to assessing head-to-door contact. The CRABI could provide a worst-case assessment of injury risk in a side impact in terms of head-to-door contact. If the CR were unable to prevent the ATD’s head from contacting the door in the test, NHTSA believes such an outcome would be a reasonable indication of an unacceptable risk of head contact of children represented by the CRABI. Accordingly, NHTSA proposes head-to-door contact as a pass-fail criterion for assessing CRs tested with the CRABI. They believe that this criterion will lead to improved side coverage. In their study, video analysis showed that only 1 out of 12 rear-facing CR models tested with the CRABI dummy had head-to-door contact during the test.

In addition, NHTSA tentatively believes that the CRABI dummy would be suitable and should be used for assessing a CR’s ability to maintain its structural integrity in side crashes when restraining 1-year-old children.

In the simulated side impact test, the CR would be required to maintain system integrity when tested with the Q3s and with the CRABI. When a CR is dynamically tested with the appropriate ATD, there could not be any complete separation of any loadbearing structural element of the CR or any partial separation exposing surfaces with sharp edges that may contact an occupant.

Applying the proposed injury criteria specified for the Q3s dummy (HIC15 ≤ 570, chest deflection ≤ 23 mm), the results of the fleet tests showed that the Q3s measured HIC15 greater than 570 in 7 of the 12 forward-facing CRs NHTSA tested. The Q3s measured chest deflection greater than 23 mm (0.91 in) in 3 of the 12 forward-facing CRs tested.

The ATD measured both HIC15 greater than 570 and chest deflection greater than 23 mm in 3 of the tests of the forward-facing CRs.

For the 5 rear-facing CRs NHTSA tested, the results of the fleet tests showed that the Q3s measured HIC15 greater than 570 in 3 of the 5 rear-facing CRs tested, and chest deflection greater than 23 mm (0.91 in) in 2 of the 5 tests. The ATD measured both HIC15 greater than 570 and chest deflection greater than 23 mm (0.91 in) in 1 of the 5 rear-facing CRs tested.

 

Exemptions

Harnesses (Vests)

NHTSA tentatively believes that harnesses should be excluded because of practicability concerns about the ability of the harness to meet the proposed requirements and because harnesses serve a need in certain populations. Harnesses would likely not be able to meet the proposed performance requirements because they do not have a side structure that can be reinforced and/or padded to mitigate forces on the Q3s in the side test. At the same time, we recognize that there is a niche served by harnesses on certain school buses and special needs buses, one whose needs cannot be met by any other type of CRS. In addition, the side-impact crash environment of a school bus is significantly different from that simulated by the proposed sled test procedure (which simulates a near-side impact of a small passenger car). Accordingly, we propose excluding harnesses from the proposed side-impact requirements.

Car beds

Car beds would also be excluded from the proposed requirements. Car beds do not “seat” children but instead restrain or position a child in a supine or prone position on a continuous flat surface. FMVSS No. 213 requires manufacturers of car beds to provide instructions stating that the car bed should be positioned in the vehicle such that the child’s head is near the center of the vehicle. We believe that, due to the supine position and location of the head of the child, the risk of injury and the injury patterns of children in car beds are much different from those of children seated forward- or rear-facing. There is no accident data available that show that benefits would accrue from applying the proposed side impact protection standard to car beds.

 

LATCH

NHTSA proposes that the child restraint’s top tether be attached during the side impact test when testing forward-facing CRs that provide a tether. NHTSA is requesting comment on whether the standard should also require testing without the top tether attached for these forward-facing CRs.

Comments are also requested on whether the standard should require CRs to meet the proposed side-impact requirements when attached to the SISA with a belt system, and on whether the belt system should be a Type I (lap) or a Type II (lap and shoulder) belt system. The original Takata sled had a Type II belt system; NHTSA modified the test bench seat to incorporate child restraint anchorages and also modified the location of the Type II belt anchorages based on their survey of vehicle rear seat geometry. Preliminary tests conducted with CRs attached to the sliding seat using the Type II belt system showed similar performance metrics to that obtained when the CRs were attached using the child restraint anchorage system, suggesting that the method of CR attachment has minimal effect on performance.

 

Potential Implications for Booster Seats

Any booster seat (or combination seat when used in booster mode) rated for a child weight of less than 40 lbs. will have to meet the new testing requirements. Since CRs sold for children weighing more than 18 kg (40 lb) would be excluded from the proposed side impact protection requirements, an approach available at no additional cost to manufacturers would be to re-label the belt-positioning seat as not recommended for children weighing less than 18 kg (40 lb). NHTSA finds this approach to be desirable in that it is aligned with their view that children under age 4 are more protected in a CR with a harness than in a belt-positioning booster. Moreover, the labeling change would increase the likelihood that children would be restrained by CRs that meet side-impact protection requirements up to 18 kg (40 lb).

Regardless of whether a manufacturer re-labels the belt-positioning seat to restrict use of the belt-positioning seat to children weighing over 18 kg (40 lb) or designs a belt-positioning seat to meet the proposed requirements, the effect of the proposed requirement would be to improve the side impact protection to children weighing less than 18 kg (40 lb).

 

Proposed Effective Date

NHTSA is proposing a lead time of 3 years from date of publication of the final rule. This means that CRs manufactured on or after the date 3 years after the date of publication of the final rule must meet the side-impact requirements. NHTSA proposes to permit optional early compliance with the requirements beginning soon after the date of publication of the final rule. NHTSA believes there is good cause for providing 3 years lead time. CR manufacturers will have to gain familiarity with the new test procedures and the new Q3s dummy, assess their products’ conformance to the FMVSS 213 side-impact test, and possibly incorporate changes into their designs. NHTSA believes that 3 years of lead time would give manufacturers sufficient time to design CRs that comply with the side impact requirements.

The 90 day public comment period opens next week.

UPDATE: December 2020

10 years later and we’re still waiting for the #$@&%*! final rule!